Measuring background atmospheric abundances and trends of the greenhouse gas nitrogen trifluoride (NF3) for the first time, a team of researchers at Scripps Institution of Oceanography at UC San Diego found that NF3 levels are at least four times higher than previously estimated.

The team, led by Scripps geochemistry professor Ray Weiss, found that the mean
global tropospheric concentration of NF3 has risen quasi-exponentially from about 0.02 ppt (parts-per-trillion) at the beginning of their measured record in 1978, to a 1 July 2008 value of 0.454 ppt, with a rate of increase of 0.053 ppt yr-1, or about 11% per year. The research will be published 31 October in Geophysical Research Letters, a journal of the American Geophysical Union (AGU).

The amount of the gas in the atmosphere, which could not be detected using previous techniques, had been estimated at less than 1,200 metric tons in 2006. The new research shows the actual amount was 4,200 metric tons. In 2008, about 5,400 metric tons of the gas was in the atmosphere.

Nitrogen trifluoride is one of several gases used during the manufacture of liquid crystal flat-panel displays, thin-film photovoltaic cells and microcircuits. Many industries have used the gas in recent years as an alternative to perfluorocarbons, which are also potent greenhouse gases, because it was believed that no more than 2% of the NF3 used in these processes escaped into the atmosphere.

This rise rate corresponds to about 620 metric tons of current NF3 emissions globally per year, or about 16% of the poorly-constrained global NF3 production estimate of 4,000 metric tons yr-1. This is a significantly higher percentage than has been estimated by industry, and
thus strengthens the case for inventorying NF3 production and for regulating its emissions.

—Weiss et al. (2008)

Emissions of NF3 were thought to be so low that the gas was not considered to be a significant potential contributor to global warming, and it is not covered by the Kyoto Protocol. The gas is 17,000 times more potent on a 100-year time horizon as a global warming agent than a similar mass of carbon dioxide, and survives in the atmosphere about five times longer than carbon dioxide. Current NF3 emissions, however, contribute only about 0.15% of the total global warming effect contributed by current human-produced carbon dioxide emissions.

Accurately measuring small amounts of NF3 in air has proven to be a very difficult experimental problem, and we are very pleased to have succeeded in this effort.

—Ray Weiss

The Scripps team analyzed air samples gathered over the past 30 years, working under the auspices of the NASA-funded Advanced Global Atmospheric Gases Experiment (AGAGE) network of ground-based stations. The network was created in the 1970s in response to international concerns about chemicals depleting the ozone layer. It is supported by NASA as part of its congressional mandate to monitor ozone-depleting trace gases, many of which are also greenhouse gases. Air samples are collected at several stations around the world. The Scripps team analyzed samples from coastal clean-air stations in California and Tasmania for this research.

The team analyzed NF3 using a modified version of the Medusa cryogenic
preconcentration and gas chromatograph/mass spectrometer (GC/MS) system. The Scripps team devised a procedure to separate NF3 in the GC/MS from more abundant volatile atmospheric gases, especially krypton (Kr) and carbon dioxide (CO2) that would otherwise quench the mass spectrometer.

The researchers found concentrations of the gas rose from about 0.02 parts per trillion in 1978 to 0.454 parts per trillion in 2008. The samples also showed significantly higher concentrations of NF3 in the Northern Hemisphere than in the Southern Hemisphere, which the researchers said is consistent with its use predominantly in Northern Hemisphere countries. The current observed rate of increase of NF3 in the atmosphere corresponds to emissions of about 16% of the amount of the gas produced globally.

As is often the case in studying atmospheric emissions, this study shows a significant disagreement between bottom-up emissions estimates and the actual emissions as determined by measuring their accumulation in the atmosphere. From a climate perspective, there is a need to add NF3 to the suite of greenhouse gases whose production is inventoried and whose emissions are regulated under the Kyoto Protocol, thus providing meaningful incentives for its wise use.

—Ray Weiss

Michael Prather is a UC Irvine atmospheric chemist who predicted earlier this year that based on the rapidly increasing use of NF3, larger amounts of the gas would be found in the atmosphere. Prather said the new Scripps study provides the confirmation needed to establish reporting requirements for production and use of the gas.

“This result reinforces the critical importance of basic research in determining the overall impact of the information technology industry on global climate change, which has already been estimated to be equal to that of the aviation industry,” added Larry Smarr, director of the California Institute for Telecommunications at UCSD, who was not involved in the Scripps study.

Comments

Oh my, it's increasing at over 54 parts per quadrillion a year. So in a million years the amount in the atmosphere will be what? And how are we supposed to respond, shut down whats left of the semiconductor industry in this country? Brilliant!

And yet with all these rising GHGs, the temperature of the planet and its oceans continues to decline. Could these greenhouse gases be starting to cool the earth instead of heating, like 1970s scientists believed? The last thing we need is an ice age that starves billions of people and causes a massive dieoff.org

2005 was the warmest year on record: http://www.msnbc.msn.com/id/11009001/

2007 tied 1998 for the 2nd warmest year on record: http://environment.about.com/b/2008/01/14/2007-second-warmest-year-on-record.htm

"The eight warmest years in the GISS record have all occurred since 1998, and the 14 warmest years in the record have all occurred since 1990."
http://www.nasa.gov/topics/earth/features/earth_temp.html

Having worked with NF3 and the gases it replaced, for over 20 years in the semiconductor and FPD industries, I would like to add some perspective. Perfluorinated compounds have been widely used for several decades in the manufacture of semiconductors, and more recently in FPD and solar panel fabrication. The primary use for these chemicals is for cleaning residual glass deposition from the chamber walls of the processing equipment. The gases are energetically broken down via RF plasma excitation to produce very reactive and short lived atomic fluorine which reacts with the silicon containing residues converting them to gaseous byproducts which are pumped away by vacuum pumps, scrubbed by exhaust capture systems, and entrained. Roughly 10 years ago, the semiconductor industry in the US, recognizing that even though their PFC emissions accounted for less than 0.02% of the world total PFC emission footprint, voluntarily took on the responsibility of curbing emissions of the worst GHG's from their industry sector. We found many cases where simple optimization of processes produced greater than 50% reductions in emissions. Substituting chemicals that had lower GWP's but produced equivalent process results also were found possible and implemented. Novel new hardware was developed and deployed that, in the case of NF3, decomposed better than 99.9% of the chemical converting it to relatively benign by-products (from a GWP perspective). We found that in addition to practically eliminating GHG emission, the new hardware produced far better manufacturing results making the adoption very palatable for industry and effectively enabling cost effective FPD manufacture. Having contributed to numerous analytical emission studies of NF3 and other PFC's, I take issue with Weiss's assertion that NF3 emission accounts for 0.15% of all human attributable GHG's. His estimate is most probably off by at least 2 decades. As a final point, analytical methods that are claimed to resolve in the parts per quadrillion range should be viewed with extreme skepticism until a suitable track record is established.

no we must stop all semiconductor work here! only China and India can produce NF3 its not fair that we produced so much and have such lower populations. we must kill our industries and let China and India pollute at will since there per capita emmissions are so much less its only fair...